| Kirk Mellish's Weather Commentary |
Things that make up a long-range winter forecast
Pacific
1) ENSO Cycle (+0.7 to +1.0 C as of 10/12/09): defined as current status of the El Nino Southern Oscillation Cycle as reported by the US Climate Prediction Center in a brief diagnostic discussion as well as the weekly ENSO update.
2) PDO Index (positive phase as of 10/8/09): The Pacific Decadal Oscillation is defined as monitoring the "leading principal component of North Pacific monthly sea surface temperature variability (poleward of 20N for the 1900-93 period)." Researchers at the University of Washington suggest that "combining ENSO and PDO information may enhance the skill of empirical North American climate forecasts." Sources: UWA, Climate Impacts Group.
Atlantic
1) SSTA (Data pending): Defined as sea surface temperature anomalies for the Gulf of Mexico and West Atlantic. The American Meteorological Society states in a February 2003 journal article that "Using a combination of statistical methods and monthly SST anomalies (SSTAs) from one or two ocean regions" there are strong correlations between sea surface temperatures and precipitation during much of the year in the United States."
2) 2009 Hurricane Season (Data pending): Defined as the frequency and track of tropical cyclones in the Atlantic basin. It is hypothesized for discussion that a less active hurricane season combined with a positive ENSO cycle may correlate to increased probability of significant winter storms in the Eastern United States in the following six month period from October to March. Historical data supporting this hypothesis will be provided.
B) Cryosphere (Monitoring specific data sets about the frozen part of the northern hemisphere's polar water system)
1. Arctic sea ice (5.27 mil sq. km as of 9/28): Defined as the total surface area in million square kilometers of sea ice within the Arctic Circle as reported weekly by the National Ice Center.
2. N. Hemispheric snow cover (data pending): Defined as a visual interpretation and data on extent of snow cover across the United States, Canada, Russia, Northern Asia and Europe
C) Atmospheric Data (Monitoring quantitative indices which track variability in atmospheric teleconnective patterns, such as how might air pressure changes over Greenland affect the track of a US East coast storm). Note: Data and info for this section posted later Sunday.
NAO: North Atlantic Oscillation Index (my preferred "local teleconnection" that reveals much about current weather, upcoming pattern changes, storm tracks and cold outbreaks)
PNA: Pacific-North American Index
MJO: Madden-Julian Oscillation Index (wildly intriguing atmospheric hiccup that has been suggested by some is a major factor in the ENSO cycle-- details later.)
QBO: Quasi-Biennial Oscillation Index (interesting pattern relationships between easterly or westerly phase of this index, current solar cycle and latitude variation of North Atlantic winter storms.) Source: 1988 article in the journal Geophysical Research Letters.
now this one's a toughie..
AAM: Axial Angular Momentun of the Atmosphere. (you better take some Tylenol before we go over this.)
D) Solar Cycle (data pending): Defined as the monthly mean, frequency and duration of sun spots as an influential factor in Earth climate)
- Solar cycle status similar to 1901-03, similar anomalous Autumn temps.
BASIC PROJECTIONS: The current "lakes cutter" pattern I believe will shift back to the East Coast within two weeks. If this shift aligns with several climate teleconnections that suggest a return to cold EVEN BEFORE 11/15, the potential remains for a surprisingly early arrival of significant winter weather into the Mid-Atlantic.
GENERAL CLIMATE & WEATHER TRENDS: The fading and less-than-active hurricane season has permitted sea surface temperatures in the Gulf of Mexico and western Atlantic to remain at or above normal. This has enhanced warm moisture advection into developing systems. The biggest Colorado snowstorm in 12 years is continuing evidence of this trend, clearly demonstrating the influence a strong subtropical jet can have in delivering moisture from the the East Pacific. Other indicators:
This nice write up is provided by Science teacher Mr. Foot of Baltimore County Schools.
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